Asteroids AR voltage issue

bungy

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The AR board in my Asteroids was off by a couple volts, so I ordered Bob Roberts' shotgun repair kit and a big blue. Voltages check fine at the power brick, but I get 5.6 to 6.6 on the AR board through the range allowed by the pot at R8. I'm trying to figure out why the voltage won't get closer to 5v. There don't seem to be any missing or burned parts on the board. Any ideas on what to check / replace next?

This board looks like the 01 revision of A034485.
 
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I've learned a lot about these over the last few days!

Are you measuring with a load (pcb connected)?

Make that two of us! I just checked it with the PCB connected and it was under 4. Dialed it right up to 5 with room to spare. I guess this thing is working the way it's supposed to. Thanks!
 
Great!

I learned that there is a HUGE range of voltages without the load. With it, and you are risking the damage to your pcb (if the voltages are really off), you get the best readings!

Congrats!
 
Before I tested this board, I happened to check the AR board in my Asteroids Deluxe and it read 12+ volts with no load and the pot did nothing. I nearly threw it across the room! I was wondering all day how the game could work fine, and when I looked closer at the board I could see someone had hacked it a little. I went back and hooked up the PCB and checked the voltage at the PCB and it was just under 5v. I was able to adjust it back up to 5 with the pot. Obviously there is a little black magic going on.

So yeah, I guess the best readings are with a load. Thanks again!
 
FYI... I had an A/R II reading +13vdc at the Molex connection when it was not hooked up to the PCB. R29 was open! I replaced it and then was able to set up the P/S before hooking it back up to the PCB.
Jeff
 
FYI... I had an A/R II reading +13vdc at the Molex connection when it was not hooked up to the PCB. R29 was open! I replaced it and then was able to set up the P/S before hooking it back up to the PCB.
Jeff

Just an FYI...An Atari A/R II will regulate (somewhat) without a load. You might have to bump up the 5VDC pot after a load is supplied....but you can test it without a load.

An Atari A/R I will not regulate without a load. On a working A/R I, the 5VDC line will always read high without a load (usually 6VDC...give or take .5VDC).

Now, if the sense mod has been done (which, I do not recommend) to a A/R I....it will regulate without a load.

Edward
 
Just an FYI...An Atari A/R II will regulate (somewhat) without a load. You might have to bump up the 5VDC pot after a load is supplied....but you can test it without a load.

An Atari A/R I will not regulate without a load. On a working A/R I, the 5VDC line will always read high without a load (usually 6VDC...give or take .5VDC).

Both boards regulate perfectly well without a load... the difference being that the voltage drop across the shunt resistors between +5/+sense and gnd/-sense are almost nothing since the current sunk by the sense pin on the regulator is very low, so you'll see +5 on the sense line with +5 on the outputs.

The AR1 uses diodes instead of resistors to shunt between power and sense, so without a real sense path through the board, you need a couple diode drops above 5V on the output to get 5V on the sense line.

Might be worth making a dummy load PCB w/ the semi-standard atari power pinout for testing ARIIs along w/ the harness and edge connectors.
 
Both boards regulate perfectly well without a load... the difference being that the voltage drop across the shunt resistors between +5/+sense and gnd/-sense are almost nothing since the current sunk by the sense pin on the regulator is very low, so you'll see +5 on the sense line with +5 on the outputs.

The AR1 uses diodes instead of resistors to shunt between power and sense, so without a real sense path through the board, you need a couple diode drops above 5V on the output to get 5V on the sense line.

Might be worth making a dummy load PCB w/ the semi-standard atari power pinout for testing ARIIs along w/ the harness and edge connectors.

Hey Mark,
I've never had a working AR1 give me a regulated 5VDC unloaded.....it's always around 6-6.5VDC (unless someone's hacked the sense mod onto it).

Edward
 
Hey Mark,
I've never had a working AR1 give me a regulated 5VDC unloaded.....it's always around 6-6.5VDC (unless someone's hacked the sense mod onto it).

Just because it's not 5V doesn't mean it's not being regulated :)
Like I said, it's being regulated to 5V + 2 diode drops ~= 6-6.5V....
 
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